Real-world effectiveness and safety of CT-P13, an infliximab biosimilar, for inflammatory bowel diseases: A prospective national observational cohort study (ReFLECT study).

BACKGROUND: ReFLECT was a French, prospective, multicenter, observational cohort study evaluating the effectiveness and safety of the infliximab (IFX) biosimilar CT-P13 in a real-world setting. Here, we describe the results for adults with inflammatory bowel disease (IBD). METHODS: Eligible patients with IBD were recruited and received intravenous CT-P13 induction and/or maintenance therapy; patients were either naive to IFX (IFX-naive) or previously treated with IFX originator or another IFX biosimilar (IFX-switched). The primary objective was CT-P13 persistence, which was measured as a time-dependent variable during a two-year follow-up period with four prespecified visits. Safety was assessed. RESULTS: The adult IBD population comprised 530 patients with Crohn's disease (CD), including 327 categorized as IFX-naive, 188 as IFX-switched, 11 as other (i.e., previously received IFX but received another treatment before switching to CT-P13), and 4 with missing data; and 221 patients with ulcerative colitis (UC), including 152 categorized as IFX-naive, 59 as IFX-switched, 8 as other, and 2 with missing data. After two years of follow-up, the rates of CT-P13 persistence were 71.7% (95% CI: 66.7, 77.0) and 63.7% (55.3, 73.3) in patients with CD and UC, respectively. CT-P13 persistence was greater for IFX-switched patients than for IFX-naive patients (CD: 83.7% [95% CI: 78.0, 89.9] vs 65.7% [58.6, 73.7]; UC: 91.2% [81.7, 100.0] vs 53.4% [43.0, 66.2]). The main reason for CT-P13 discontinuation was loss of response (CD/UC) in both IFX-naive (14.7%/21.7%) and IFX-switched (7.4%/5.1%) groups. Among patients (CD and UC, respectively), 51.3% and 45.2% reported ≥1 adverse event (AE), and 13.2% and 12.7% reported serious AEs, respectively. CONCLUSION: After two years of follow-up, the effectiveness of intravenous CT-P13 was maintained in >80% of IFX-switched patients. CT-P13 induced effective therapeutic maintenance in IFX-naive patients. CT-P13 had an acceptable safety profile. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02925338.

CIC/ATXN1-rearranged tumors in the central nervous system are mainly represented by sarcomas: A comprehensive clinicopathological and epigenetic series.

CIC fusions have been described in two different central nervous system (CNS) tumor entities. On one hand, fusions of CIC or ATXN1 genes belonging to the same complex of transcriptional repressors, were reported in the CIC-rearranged, sarcoma (SARC-CIC). The diagnosis of this tumor type, which was recently added to the World Health Organization (WHO) Classification of CNS tumors, is difficult mainly because the data concerning its histopathology (as compared to its soft tissue counterpart), immunoprofile, and clinical as well as radiological characteristics are scarce in the literature. On the other hand, a recent study, based on DNA-methylation profiling, has identified a novel high-grade neuroepithelial tumor characterized by recurrent CIC fusions (HGNET-CIC). The aim of this multicentric study was to characterize a cohort of 15 primary CNS tumors harboring a CIC or ATXN1 fusion in terms of clinical, radiological, histopathological, immunophenotypical, and epigenetic characteristics. According to the integrated diagnoses, 14/15 tumors corresponded to SARC-CIC, and only one to HGNET-CIC. The tumors showed similar clinical (mainly pediatric), radiological (mostly supratentorial, cystic, and contrast enhancing), immunophenotypical (common expression of glioneuronal markers), and genetic (similar spectrum of fusions) profiles but their histopathological appearance was clearly distinct. Moreover, we found a novel fusion transcript (CIC::EWSR1) in a SARC-CIC. Most DNA methylation profiles using the Heidelberg Brain Tumor Classifier (v12.8) annotated the samples to the methylation class "SARC-CIC" (9/14 tumors with available data). By using uniform manifold approximation and projection analysis, four other samples were classified as SARC-CIC and another clustered within the methylation class of HGNET-CIC. Our findings confirm that CNS CIC-fused tumors do not represent a single molecular tumor entity. Further analyses are needed to characterize HGNET-CIC in more detail. These results may help to refine the essential diagnostic criteria for SARC-CIC and their terminology (with a suggested consensual name of sarcoma, CIC/ATXN1-complex rearranged).

A Clinico-Genetic Score Incorporating Disease-Free Intervals and Chromosome 8q Copy Numbers: A Novel Prognostic Marker for Recurrence and Survival Following Liver Resection in Patients with Liver Metastases of Uveal Melanoma.

Surgical treatment of liver metastases of uveal melanoma (LMUM) could be proposed for selected patients. This retrospective study examined the prognostic significance of the genetic profiles of liver metastases after LMUM resection. A total of 86 patients treated with resection for LMUM, who underwent genetic analysis of liver metastasis, were included. A multivariable Cox model identified the independent predictors of recurrence-free survival (RFS) and overall survival (OS). The disease-free interval (DFI) and a chromosome 8q surgain (>3 copies) were independent predictors and categorized patients into three risk groups with distinct postoperative prognoses. For the low-, intermediate-, and high-risk scores of recurrence, the median RFS values were 15 months (95% CI: 10-22), 6 months (95% CI: 4-11), and 4 months (95% CI: 2-7), and the median OS values were 86 months (95% CI: 55-NR), 25 months (95% CI: 17-48), and 19 months (95% CI: 12-22), respectively. The predictive accuracy of this scoring system was demonstrated by a mean area under the curve (AUC(t)) of 0.77 (95% CI: 0.65-0.90) for RFS and 0.81 (95% CI: 0.70-0.92) for OS. This novel score, based on a DFI of ≤24 months combined with a chromosome 8q surgain, identifies patients at a high risk of early recurrence and could help clinicians to propose perioperative treatment.

Prospective assessment of circulating tumor DNA in patients with metastatic uveal melanoma treated with tebentafusp.

Tebentafusp, a bispecific immune therapy, is the only drug that demonstrated an overall survival benefit in patients with metastatic uveal melanoma (MUM). Circulating tumor DNA (ctDNA) has emerged as a potential prognostic and predictive marker in the phase 3 IMCgp100-202 trial using multiplex PCR-based next-generation sequencing (NGS). In this study (NCT02866149), ctDNA dynamics were assessed using droplet digital PCR (ddPCR) in 69 MUM patients undergoing tebentafusp treatment. Notably, 61% of patients exhibited detectable ctDNA before treatment initiation, which was associated with shorter overall survival (median 12.9 months versus 40.5 months for patients with undetectable ctDNA; p < 0.001). Patients manifesting a 90% or greater reduction in ctDNA levels at 12 weeks demonstrated markedly prolonged overall survival (median 21.2 months versus 12.9 months; p = 0.02). Our findings highlight the potential of ddPCR-based ctDNA monitoring as an economical, pragmatic and informative approach in MUM management, offering valuable insights into treatment response and prognosis.

Cellular origin and clonal evolution of human dedifferentiated liposarcoma.

Dedifferentiated liposarcoma (DDLPS) is the most frequent high-grade soft tissue sarcoma subtype. It is characterized by a component of undifferentiated tumor cells coexisting with a component of well-differentiated adipocytic tumor cells. Both dedifferentiated (DD) and well-differentiated (WD) components exhibit MDM2 amplification, however their cellular origin remains elusive. Using single-cell RNA sequencing, DNA sequencing, in situ multiplex immunofluorescence and functional assays in paired WD and DD components from primary DDLPS tumors, we characterize the cellular heterogeneity of DDLPS tumor and micro-environment. We identify a population of tumor adipocyte stem cells (ASC) showing striking similarities with adipocyte stromal progenitors found in white adipose tissue. We show that tumor ASC harbor the ancestral genomic alterations of WD and DD components, suggesting that both derive from these progenitors following clonal evolution. Last, we show that DD tumor cells keep important biological properties of ASC including pluripotency and that their adipogenic properties are inhibited by a TGF-ß-high immunosuppressive tumor micro-environment.

E-Cadherin Mutational Landscape and Outcomes in Breast Invasive Lobular Carcinoma.

Invasive lobular carcinomas (ILC) are characterized by the loss of E-cadherin expression and CDH1 gene inactivation. Diagnostic reproducibility for this tumor type is currently suboptimal and could be improved by a better understanding of its histomolecular and clinical heterogeneity. We have analyzed the relationship between the presence, type, or position of CDH1 mutations, E-cadherin expression, and clinicopathological features (including outcome) in a retrospective series of 251 primary ILC with a long follow-up (median: 9.5 years). The mutational status of E-cadherin gene (CDH1) was determined by RNA sequencing from frozen tumor samples. E-cadherin immunohistochemistry (IHC) was performed with antibodies directed against the intracellular domain (clone 4A2C7) and the extracellular domain (clone NCH38). IHC expression of p120 and ß-catenin was also assessed in E-cadherin diffusely positive cases. Three major patterns of E-cadherin membrane expression were identified by IHC, with good agreement between the 2 clones (overall concordance: 83.8%, Kappa 0.67): null/focal expression (≤10%) (72.8% of cases for 4A2C7 and 83.8% for NCH38), heterogeneous expression (11%-89%) (19.2% of cases for 4A2C7 and 6.9% for NCH38), and diffuse expression (≥90%) (8% of cases for 4A2C7 and 9.3% for NCH38). E-cadherin membranous expression, when present, was abnormal (incomplete labeling and/or reduced intensity). ILC with diffuse E-cadherin expression showed abnormal ß-catenin or p120-catenin staining in 21% of cases. Interestingly, these cases with diffusely expressed E-cadherin had a CDH1 mutation rate as high as the E-cadherin null/focal cases (∼70%) but were enriched in nontruncating mutations. Regarding CDH1 mutation location, intracytoplasmic domain mutations correlated with a divergent E-cadherin IHC phenotype between the 2 antibodies (4A2C7 ≤ 10%/NCH38 ≥ 10%). Clinico-pathological correlation analyses found that stromal amount (inversely correlated with tumor cellularity) and tumor-infiltrating lymphocytes were less abundant in ILC with E-cadherin null/focal cases. In addition, CDH1 truncating mutations were associated with radiohistologic size discordance and were identified in multivariate survival analysis as an independent poor prognosis factor in terms of metastasis risk and breast cancer-related mortality. Overall, our study highlights the importance of the precise mutational status of CDH1 in the clinical, radiological, histologic, and phenotypic expression of lobular carcinomas. These findings should be taken into account in future attempts to improve diagnostic criteria or methods for ILC, as well as for clinicobiological studies dedicated to this tumor type.

Alveolar soft part sarcomas in young patients: The French national NETSARC+ network experience.

BACKGROUND AND AIMS: Alveolar soft part sarcoma (ASPS) is an ultra-rare chemo-resistant sarcoma in children, occurring preferentially in young adults. We aimed to describe and compare its clinical presentation and behaviour in children and young adults to determine whether the same therapeutic strategy should be addressed for both populations. METHODS: National retrospective multicentre study of children (0-18 years) vs. young adults (19-30 years) included in the "ConticaBase" sarcoma database, treated for ASPS between 2010 and 2019 with pathology reviewed via the NETSARC + network. RESULTS: Overall, 45 patients were identified, 19 children (42%) and 26 young adults (58%). All ASPS diagnoses were confirmed with TFE3 rearrangement by immunohistochemistry or FISH. All clinical characteristics were balanced between both populations with frequent metastases at diagnosis (8/19 vs. 10/26). The therapeutic strategy was based on surgery (17/19 vs. 21/26), radiotherapy (8/19 vs. 12/26) ± systemic treatment (8/19 vs. 9/26). In patients with initially localized disease, metastatic relapse occurred only in adults (8/16), whereas metastatic progression was present in both metastatic groups (5/8 vs. 8/10). After a median follow-up of 5.2 years (range, 0.2-12.2), 5-year EFS was 74% [95%CI, 56-96] vs. 47% [30-74] (p = 0.071) respectively, and 5-year OS was 95% [85-100] vs. 85% [70-100] (p = 0.84). For localized tumours, 5-year MFS was 100% [100-100] vs. 60% [39-91] (p = 0.005). The 5-year OS of all patients with metastasis at diagnosis was 80.2% (62.2%-100%). CONCLUSIONS: ASPS appears to have the overall same clinical characteristics, but a more aggressive behaviour in young adults than in children. However, despite frequent metastases at diagnosis, long-term survival is high in both groups. Overall, the same therapeutic strategies may be considered for both populations.

Diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters (DGONC), new name and new problems: an illustration of one case with atypical morphology and biology.

A novel histomolecular tumor of the central nervous system (CNS), the "diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters (DGONC)," has recently been identified, based on a distinct DNA methylation profile and has been added to the 2021 World Health Organization Classification of CNS Tumors. This glioneuronal tumor mainly affects the supratentorial area in children and recurrently presents with a monosomy of chromosome 14. Herein, we report the case of a DNA-methylation based diagnosis of DGONC having atypical features, such as pseudo-rosettes and the absence of a chromosome 14 monosomy, thus rendering its diagnosis very challenging. Because of the wide variety of morphologies harbored by DGONC, a large range of differential diagnoses may be hypothesized from benign to malignant. Interestingly, the current case, like one previously reported, exhibited a co-expression of OLIG2, synaptophysin and SOX10, without GFAP immunopositivity. This particular immunophenotype seems to be a good indicator for a DGONC diagnosis. The classification of DGONC amongst glioneuronal or embryonal tumors is still debated. The clinical (a pediatric supratentorial tumor), morphological (from a benign oligodendroglioma-like tumor with microcalcifications and possible neuropil-like islands to a malignant embryonal tumor with a possible spongioblastic pattern), and immunohistochemical (co-expression of OLIG2 and synaptophsyin) profiles resemble CNS, neuroblastoma, FOXR2-activated and may potentially bring them together in a future classification. Further comprehensive studies are needed to conclude the cellular origin of DGONC and its prognosis.

Sequential Analysis of cfDNA Reveals Clonal Evolution in Patients with Neuroblastoma Receiving ALK-Targeted Therapy.

PURPOSE: The study of cell-free DNA (cfDNA) enables sequential analysis of tumor cell-specific genetic alterations in patients with neuroblastoma. EXPERIMENTAL DESIGN: Eighteen patients with relapsing neuroblastoma having received lorlatinib, a third-generation ALK inhibitor, were identified (SACHA national registry and/or in the institution). cfDNA was analyzed at relapse for nine patients and sequentially for five patients (blood/bone marrow plasma) by performing whole-genome sequencing library construction followed by ALK-targeted ddPCR of the hotspot mutations [F1174L, R1275Q, and I1170N; variant allele fraction (VAF) detection limit 0.1%] and whole-exome sequencing (WES) to evaluate disease burden and clonal evolution, following comparison with tumor/germline WES. RESULTS: Overall response rate to lorlatinib was 33% (CI, 13%-59%), with response observed in 6/10 cases without versus 0/8 cases with MYCN amplification (MNA). ALK VAFs correlated with the overall clinical disease status, with a VAF < 0.1% in clinical remission, versus higher VAFs (>30%) at progression. Importantly, sequential ALK ddPCR detected relapse earlier than clinical imaging. cfDNA WES revealed new SNVs, not seen in the primary tumor, in all instances of disease progression after lorlatinib treatment, indicating clonal evolution, including alterations in genes linked to tumor aggressivity (TP53) or novel targets (EGFR). Gene pathway analysis revealed an enrichment for genes targeting cell differentiation in emerging clones, and cell adhesion in persistent clones. Evidence of clonal hematopoiesis could be observed in follow-up samples. CONCLUSIONS: We demonstrate the clinical utility of combining ALK cfDNA ddPCR for disease monitoring and cfDNA WES for the study of clonal evolution and resistance mechanisms in patients with neuroblastoma receiving ALK-targeted therapy.

FGFR1 fusions as a novel molecular driver in rhabdomyosarcoma.

The wide application of RNA sequencing in clinical practice has allowed the discovery of novel fusion genes, which have contributed to a refined molecular classification of rhabdomyosarcoma (RMS). Most fusions in RMS result in aberrant transcription factors, such as PAX3/7::FOXO1 in alveolar RMS (ARMS) and fusions involving VGLL2 or NCOA2 in infantile spindle cell RMS. However, recurrent fusions driving oncogenic kinase activation have not been reported in RMS. Triggered by an index case of an unclassified RMS (overlapping features between ARMS and sclerosing RMS) with a novel FGFR1::ANK1 fusion, we reviewed our molecular files for cases harboring FGFR1-related fusions. One additional case with an FGFR1::TACC1 fusion was identified in a tumor resembling embryonal RMS (ERMS) with anaplasia, but with no pathogenic variants in TP53 or DICER1 on germline testing. Both cases occurred in males, aged 7 and 24, and in the pelvis. The 2nd case also harbored additional alterations, including somatic TP53 and TET2 mutations. Two additional RMS cases (one unclassified, one ERMS) with FGFR1 overexpression but lacking FGFR1 fusions were identified by RNA sequencing. These two cases and the FGFR1::TACC1-positive case clustered together with the ERMS group by RNAseq. This is the first report of RMS harboring recurrent FGFR1 fusions. However, it remains unclear if FGFR1 fusions define a novel subset of RMS or alternatively, whether this alteration can sporadically drive the pathogenesis of known RMS subtypes, such as ERMS. Additional larger series with integrated genomic and epigenetic datasets are needed for better subclassification, as the resulting oncogenic kinase activation underscores the potential for targeted therapy.

Divergent local and systemic antitumor response in primary uveal melanomas.

Uveal melanoma (UM) is the most common cancer of the eye. The loss of chromosome 3 (M3) is associated with a high risk of metastases. M3 tumors are more infiltrated by T-lymphocytes than low-risk disomic-3 (D3) tumors, contrasting with other tumor types in which T cell infiltration correlates with better prognosis. Whether these T cells represent an antitumor response and how these T cells would be primed in the eye are both unknown. Herein, we characterized the T cells infiltrating primary UMs. CD8+ and Treg cells were more abundant in M3 than in D3 tumors. CD39+PD-1+CD8+ T cells were enriched in M3 tumors, suggesting specific responses to tumor antigen (Ag) as confirmed using HLA-A2:Melan-A tetramers. scRNAseq-VDJ analysis of T cells evidenced high numbers of proliferating CD39+PD1+CD8+ clonal expansions, suggesting in situ antitumor Ag responses. TCRseq and tumor-Ag tetramer staining characterized the recirculation pattern of the antitumor responses in M3 and D3 tumors. Thus, tumor-Ag responses occur in localized UMs, raising the question of the priming mechanisms in the absence of known lymphatic drainage.

CNS tumors with PLAGL1-fusion: beyond ZFTA and YAP1 in the genetic spectrum of supratentorial ependymomas.

A novel methylation class, "neuroepithelial tumor, with PLAGL1 fusion" (NET-PLAGL1), has recently been described, based on epigenetic features, as a supratentorial pediatric brain tumor with recurrent histopathological features suggesting an ependymal differentiation. Because of the recent identification of this neoplastic entity, few histopathological, radiological and clinical data are available. Herein, we present a detailed series of nine cases of PLAGL1-fused supratentorial tumors, reclassified from a series of supratentorial ependymomas, non-ZFTA/non-YAP1 fusion-positive and subependymomas of the young. This study included extensive clinical, radiological, histopathological, ultrastructural, immunohistochemical, genetic and epigenetic (DNA methylation profiling) data for characterization. An important aim of this work was to evaluate the sensitivity and specificity of a novel fluorescent in situ hybridization (FISH) targeting the PLAGL1 gene. Using histopathology, immunohistochemistry and electron microscopy, we confirmed the ependymal differentiation of this new neoplastic entity. Indeed, the cases histopathologically presented as "mixed subependymomas-ependymomas" with well-circumscribed tumors exhibiting a diffuse immunoreactivity for GFAP, without expression of Olig2 or SOX10. Ultrastructurally, they also harbored features reminiscent of ependymal differentiation, such as cilia. Different gene partners were fused with PLAGL1: FOXO1, EWSR1 and for the first time MAML2. The PLAGL1 FISH presented a 100% sensitivity and specificity according to RNA sequencing and DNA methylation profiling results. This cohort of supratentorial PLAGL1-fused tumors highlights: 1/ the ependymal cell origin of this new neoplastic entity; 2/ benefit of looking for a PLAGL1 fusion in supratentorial cases of non-ZFTA/non-YAP1 ependymomas; and 3/ the usefulness of PLAGL1 FISH.

Molecular and Clinical Portrait of HER2-low Invasive Lobular Carcinomas.

Invasive lobular carcinomas (ILCs) have a low frequency of ERBB2 amplification, therefore restricting the use of conventional anti-HER2 therapies for this histologic special type. Conversely, ILCs with low HER2 overexpression may represent a broader target for the use of emerging antibody drug conjugate therapies targeting HER2, since these treatments have proven effective in HER2-low breast cancers. Very scarce data about HER2-low ILCs have been so far published, although these tumors could have different prevalence and histomolecular specificities compared with invasive breast carcinoma of no special type (IBC-NST). Our aims in that context were to decipher the clinicopathological and molecular features of a large series of HER2-low ILCs. Comparative evaluation of HER2-low prevalence was done based on a retrospective series of 7970 patients from Institut Curie, with either primary invasive lobular (N = 1103) or no special type (N = 6867) invasive carcinoma. Clinicopathological and molecular analyses of HER2-zero, HER2-low, and HER2-positive ILCs were performed on a subgroup of 251 patients who underwent surgery for a primary ILC between 2005 and 2008. The mutational profile of these 251 cases was determined from RNAseq data. Compared with HER2-negative IBC-NSTs, the HER2-negative ILCs were found to display a higher frequency of HER2-zero cases (59.4% vs 53.7%) and a lower frequency of HER2-low (40.6% vs 46.3%) (P < .001). Clinicopathological features associated with HER2-low status (vs HER2-zero) in ILC were older age, postmenopausal status, nonclassic ILC histological types, higher grade, proliferation, and estrogen receptor expression levels. Survival curve analysis showed a significantly lower risk of local recurrence for HER2-low (vs HER2-zero) ILCs, but no association was found between HER2 status and either breast cancer-specific survival or distant metastasis-free interval. ERBB3 was the unique mutated gene exclusively associated with HER2-low ILCs yet being mutated at a low frequency (7.1%) (false discovery rate < 0.05). In conclusion, HER2-low ILCs exhibit their own particularities, both on clinical-pathological and molecular levels. Our findings call for larger multicenter validation studies.

Imaging characterization of paediatric tumours with the neurotrophic tyrosine receptor kinase fusion transcript.

OBJECTIVES: The neurotrophic tyrosine receptor kinase (NTRK) fusion transcript (FT) is a major genetic landmark of infantile fibrosarcoma (IFS) and cellular congenital mesoblastic nephroma (cCMN) but is also described in other tumours. The recent availability of NTRK-targeted drugs enhances the need for better identification. We aimed to describe the anatomic locations and imaging features of tumours with NTRK-FT in children. CASE SERIES: Imaging characteristics of NTRK-FT tumours of 41 children (median age: 4 months; 63% <1 year old; range: 0-188) managed between 2001 and 2019 were retrospectively analysed. The tumours were located in the soft tissues (n = 24, including 19 IFS), kidneys (n = 9, including 8 cCMN), central nervous system (CNS) (n = 5), lung (n = 2), and bone (n = 1). The tumours were frequently deep-located (93%) and heterogeneous (71%) with necrotic (53%) or haemorrhagic components (29%). Although inconstant, enlarged intratumoural vessels were a recurrent finding (70%) with an irregular distribution (63%) in the most frequent anatomical locations. CONCLUSION: Paediatric NTRK-FT tumours mainly occur in infants with very variable histotypes and locations. Rich and irregular intra-tumoural vascularization are recurrent findings. ADVANCES IN KNOWLEDGE: Apart from IFS of soft tissues and cCMN of the kidneys, others NTRK-FT tumours locations have to be known, as CNS tumours. Better knowledge of the imaging characteristics may help guide the pathological and biological identification.

CNS erythroblastic sarcoma: a potential emerging pediatric tumor type characterized by NFIA::RUNX1T1/3 fusions.

Erythroblastic sarcoma (ES) (previously called chloroma or granulocytic sarcoma) are rare hematological neoplams characterized by the proliferation of myeloid blasts at extramedullary sites, and primarily involve the skin and soft tissue of middle-aged adults. ES may be concomitant with or secondary to myeloid neoplasms (mostly acute myeloid leukemia (AML)) or in isolated cases (de novo) without infiltration of the bone marrow by blasts. ES share cytogenetic and molecular abnormalities with AML, including RUNX1T1 fusions. Some of these alterations seem to be correlated with particular sites of involvement. Herein, we report an isolated erythroblastic sarcoma with NFIA::RUNX1T1 located in the central nervous system (CNS) of a 3-year-old boy. Recently, two pediatric cases of CNS MS with complete molecular characterization have been documented. Like the current case, they concerned infants (2 and 3 years-old) presenting a brain tumor (pineal involvement) with leptomeningeal dissemination. Both cases also harbored a NFIA::RUNX1T3 fusion. ES constitutes a diagnostic challenge for neuropathologists because it does not express differentiation markers such as CD45, and may express CD99 which could be confused with CNS Ewing sarcoma. CD43 is the earliest pan-hematopoietic marker and CD45 is not expressed by erythroid lineage cells. E-cadherin (also a marker of erythroid precursors) and CD117 (expressed on the surface of erythroid lineage cells) constitute other immunhistochemical hallmarks of ES. The prognosis of patients with ES is similar to that of other patients with AML but de novo forms seem to have a poorer prognosis, like the current case. To conclude, pediatric ES with NFIA::RUNX1T1/3 fusions seem to have a tropism for the CNS and thus constitute a potential pitfall for neuropathologists. Due to the absence of circulating blasts and a DNA-methylation signature, the diagnosis must currently be made by highlighting the translocation and expression of erythroid markers.

Imaging and multi-omics datasets converge to define different neural progenitor origins for ATRT-SHH subgroups.

Atypical teratoid rhabdoid tumors (ATRT) are divided into MYC, TYR and SHH subgroups, suggesting diverse lineages of origin. Here, we investigate the imaging of human ATRT at diagnosis and the precise anatomic origin of brain tumors in the Rosa26-CreERT2::Smarcb1flox/flox model. This cross-species analysis points to an extra-cerebral origin for MYC tumors. Additionally, we clearly distinguish SHH ATRT emerging from the cerebellar anterior lobe (CAL) from those emerging from the basal ganglia (BG) and intra-ventricular (IV) regions. Molecular characteristics point to the midbrain-hindbrain boundary as the origin of CAL SHH ATRT, and to the ganglionic eminence as the origin of BG/IV SHH ATRT. Single-cell RNA sequencing on SHH ATRT supports these hypotheses. Trajectory analyses suggest that SMARCB1 loss induces a de-differentiation process mediated by repressors of the neuronal program such as REST, ID and the NOTCH pathway.

Patient Derived Xenografts (PDX) Models as an Avatar to Assess Personalized Therapy Options in Uveal Melanoma: A Feasibility Study.

Uveal melanoma is the most common primary intraocular malignancy in adults. Up to 50% of UM patients develop metastatic disease, usually in the liver. When metastatic, the prognosis is poor, and few treatment options exist. Here, we investigated the feasibility of establishing patient-derived xenografts (PDXs) from a patient's tumor in order to screen for therapies that the patient could benefit from. Samples obtained from 29 primary tumors and liver metastases of uveal melanoma were grafted into SCID mice. PDX models were successfully established for 35% of primary patient tumors and 67% of liver metastases. The tumor take rate was proportional to the risk of metastases. PDXs showed the same morphology, the same GNAQ/11, BAP1, and SF3B1 mutations, and the same chromosome 3 and 8q status as the corresponding patient samples. Six PDX models were challenged with two compounds for 4 weeks. We show that, for 31% of patients with high or intermediate risk of metastasis, the timing to obtain efficacy results on PDX models derived from their primary tumors was compatible with the selection of the therapy to treat the patient after relapse. PDXs could thus be a valid tool ("avatar") to select the best personalized therapy for one third of patients that are most at risk of relapse.

Sequential genomic analysis using a multisample/multiplatform approach to better define rhabdomyosarcoma progression and relapse.

The genomic spectrum of rhabdomyosarcoma (RMS) progression from primary to relapse is not fully understood. In this pilot study, we explore the sensitivity of various targeted and whole-genome NGS platforms in order to assess the best genomic approach of using liquid biopsy in future prospective clinical trials. Moreover, we investigate 35 paired primary/relapsed RMS from two contributing institutions, 18 fusion-positive (FP-RMS) and 17 fusion-negative RMS (FN-RMS) by either targeted DNA or whole exome sequencing (WES). In 10 cases, circulating tumor DNA (ctDNA) from multiple timepoints through clinical care and progression was analyzed for feasibility of liquid biopsy in monitoring treatment response/relapse. ctDNA alterations were evaluated using a targeted 36-gene custom RMS panel at high coverage for single-nucleotide variation and fusion detection, and a shallow whole-genome sequencing for copy number variation. FP-RMS have a stable genome with relapse, with common secondary alterations CDKN2A/B, MYCN, and CDK4 present at diagnosis and impacting survival. FP-RMS lacking major secondary events at baseline acquire recurrent MYCN and AKT1 alterations. FN-RMS acquire a higher number of new alterations, most commonly SMARCA2 missense mutations. ctDNA analyses detect pathognomonic variants in all RMS patients within our collection at diagnosis, regardless of type of alterations, and confirmed at relapse in 86% of FP-RMS and 100% FN-RMS. Moreover, a higher number of fusion reads is detected with increased disease burden and at relapse in patients following a fatal outcome. These results underscore patterns of tumor progression and provide rationale for using liquid biopsy to monitor treatment response.